1. Field of the Invention
This invention relates to a method for handling maleimides. More particularly, it relates to a method for handling, as in the process of transportation and storage, maleimides fast in a molten state proofed against coloration. Still more particularly, it relates to a method for safely and easily handling maleimides in a state proofed against coloration and polymerization.
2. Description of the Prior Art
The maleimides are compounds which are useful as raw materials for resins, medicines, and agricultural pesticides.
Heretofore, the maleimides which are solid at normal room temperature have been generally handled in the form of powder, flakes, and tablets. The maleimides in such a form entrain minute particles of themselves. Particularly during the transportation of such solid maleimides, the maleimides undergo gradual comminution and give rise to minute maleimide particles in a large amount.
The maleimides themselves possess a property of stimulating the human body. Particularly when a maleimide in the form of a fine powder is inhaled by a man, it stimulates the nasal cavity and the throat of the man and compels him to cough or sneeze. When this maleimide powder is suffered to adhere to the skin of a man and remain thereon, it causes inflammation of the affected area of his skin. The maleimides possess this undesirable quality. A man engaging in the work of handling a maleimide containing minute particles of itself, therefore, must pay rigid attention to keeping his skin from contact with the maleimide to the fullest possible extent.
Enormous labors, therefore, are required for the purpose of precluding the occurrence of minute particles of a maleimide to the fullest possible extent during the transportation of the maleimide or for the purpose of removing minute particles from the maleimide after the transportation.
When a solid substance is transported, it is packed in paper bags, drums, or other similar containers prior to the transportation in most cases. When the solid substance is a maleimide in this case, a man engaging in the transportation inevitably exposes his body to the maleimide and consequently suffers from adhesion of minute particles of the maleimide to his skin.
An attempt at conveying a solid substance by a pipeline for the purpose of preventing the solid substance from contacting the human body is fundamentally difficult to implement. Since the solid substance in conveyance has the possibility of clogging the pipeline, for example, the particles of the solid substance are subject to exacting restrictions as to shape, size, and specific gravity in order for the solid substance to be safely conveyed.
Thus, it is only logical to conclude that the transportation or conveyance of a maleimide which is solid at normal room temperature entails numerous problems. The same thing holds good with respect to the method to be employed for the storage of a solid maleimide.
As means for the solution of the problems mentioned above, methods which reside in handling maleimides in process of transportation or storage in the form of a solution in acrylonitrile, styrene, or a (meth)acrylic acid ester have been disclosed in JP-A-62-162,1167(1987), JP-A-62-143,911(1987), JP-A-62-145,062(1987), and JP-A-63-(1988)-316,767. These method are free from the occurrence of minute particles of maleimides detrimental to the human body and, therefore, may well be called excellent means as compared with the method which handle maleimides in a solid state. When the maleimides are handled in the form of a highly concentrated solution, these methods require a high temperature for the reduction of solid maleimides into the solution. Since the solvent to be used for the solution is a compound which in itself possesses an ability to polymerize, the produced maleimide solution cannot be long retained intact at the elevated temperature. To be specific, the maleimide solution suffers the occurrence of impuries such as the polymer of the solvent itself and the copolymer of the solvent with the maleimide used as a solute. These impurities cause coloration of the solution. This solution in its unmodified form is subjected to adjustment of concentration and then, as a heatresistance improving agent for ABS resin, AAS resin, AS resin, or ACS resin, for example, used for copolymerization with a monomer destined to form such a resin. When the maleimide solution to be used in this case happens to be colored as described above, the finished product is inevitably colored and consequently degraded heavily in commodity value.
The conventional methods which handle maleimides in the form of a solid or a solution, therefore, hardly deserve to be called perfect means.
An object of this invention, therefore, is to provide a novel method for handling a maleimide.
Another object of this invention is to provide a method for safe and simple transportation or storage of a maleimide without any possibility of the maleimide producing minute particles of itself during the course of transportation or storage.
Yet another object of this invention is to provide a method for handling a maleimide in such a manner as to be prevented from coloration and allowed to retain its quality intact for a long time.